高损伤阈值三倍频分离膜

 设计了Nd：YAG激光用三倍频分离膜,膜层材料为SiO₂和HfO₂。经过优化,膜系在355 nm处的反射率在99%以上,在532 nm和1 064 nm处透射率也在99%以上。采用电子束蒸发技术,在熔融石英基底上制备了样品,经测量,制备的分离膜光学性能与设计值接近。分离膜在355 nm激光辐照下的损伤阈值为5.1 J/cm²,并用微分干涉显微镜表征了薄膜损伤形貌。     

高抗激光损伤阈值介孔SiO2 减反射膜

 用P123作模板剂,通过正硅酸乙酯的水解缩聚和溶剂蒸发自组装过程在K9玻璃上制备介孔SiO₂膜。应用FT-IR,XRD,N₂ 吸附-脱附,AFM和UV-Vis表征手段研究了薄膜的介孔结构和光学性能,并使用“R-on-1”模式,以Nd:YAG脉冲激光（9.2 ns, 1 064 nm）测试了薄膜的激光损伤阈值。结果表明:所镀制单层介孔SiO₂膜具有规整的2D p6 mm长周期结构,为SBA-15型,膜层表面比较平整（均方根粗糙度为2.923 nm）,在1 064 nm处的透过率为99.5%, 换算为激光脉宽为1 ns时,膜层的激光损伤阈值为21.6 J/cm²,显示出了较好的减反性能和抗激光损伤性能。     

储存环自由电子激光器与KrF激光驱动器的激光谐振腔光学膜系实验研究

惯性约束核聚变氟化氪激光驱动器与储存环自由电子激光器,虽然其激光产生机理完全不同,但是它们对于激光谐振腔光学膜系的要求却几乎完全相同.新研制的Al₂O₃/SiO₂/MgF₂“双氧化物+单氟化物”紫外光学膜系,在248nm中心波长处,它的光学透射率测量值为0.27%—0.71%,反射率的计算值为96.5%,其光谱带宽为22.6nm.在脉冲宽度为23ns的KrF激光照射下,它的抗激光损伤阈值达到(5.36±0.30)J/cm²,是可用于储存环紫外波长自由电子激光研究与数千焦耳数量级高能、高功率KrF激光驱动器研究的高破坏阈值紫外光学膜系.     

层间热处理对SiO2/ZrO2双层膜的影响

 以正硅酸乙酯和丙醇锆为前驱体,用溶胶-凝胶法在K9基片上提拉镀制SiO₂/ZrO₂双层膜。采用不同实验步骤制备了2个样品,样品1镀完SiO₂后直接镀ZrO₂ ,样品2镀完SiO₂经热处理后再镀ZrO₂。采用原子力显微镜、椭偏仪、紫外-可见分光光度计对薄膜进行表征。针对SiO₂/ZrO₂双层膜,考虑到膜间渗透的影响,采用３层Cauchy模型进行椭偏模拟,椭偏参数的模拟值曲线与椭偏仪的测量值曲线十分吻合,进而发现热处理可以使SiO₂/ZrO₂双层膜之间的渗透减少近23 nm,从而提高其峰值透射率。利用输出波长1.064 mm,脉宽8.1 ns的激光束对样品进行了损伤阈值的测试,用光学显微镜观察损伤形貌,结果发现两者损伤阈值分别为13.6 J/c2和14.18 J/cm²,均为膜的本征损伤。     

电子通量对ZnO/K2SiO3热控涂层光学性能的影响

 研究了电子通量对ZnO/K₂SiO₃热控涂层光学性能的影响。分别采用通量为5×10¹¹/cm²·s，8×10¹¹/cm²·s，1×10¹²/cm²·s 和5×10¹²/cm²·s的电子对试样进行辐照。电子辐照下涂层的光学性能发生了退化，并且发现了退化涂层在空气中的“漂白”现象。分析了ZnO/K₂SiO₃热控涂层光学性能的退化机制，同时讨论了电子通量对太阳光谱吸收系数的影响。实验结果发现，在5×10¹¹～1×10¹²/cm²·s的电子通量范围内，电子通量对ZnO/K₂SiO³热控涂层光学性能的影响相同。因此在这个电子通量范围内，采用加速地面试验来模拟空间的电子辐照效应是有效的。     

酸碱分步催化对溶胶-凝胶ZrO2膜光学性能的影响

 以丙醇锆作为前驱体,利用酸碱分步催化法制备了ZrO₂溶胶,用粒度仪检测胶体粒度;用N₂吸脱附表征凝胶的结构;采用旋转镀膜法在K9基片上镀制单层ZrO₂薄膜;用分光光度计和椭偏仪检测膜层的透过率、折射率及膜层厚度;用红外光谱仪检测胶体内部粒子间化学键状态。实验结果发现,在脉宽1 nm,波长1 064 nm时,采用此种胶体镀制的单层ZrO2膜层折射率达到1.74,单层膜损伤阈值为9.0 J/cm²,表明该方法集中了酸与碱两种催化方式的优点,一定程度上提高了膜层的光学性能。     

SiO2内保护层对LiB3O5晶体倍频增透膜损伤阈值的影响

 利用离子辅助电子束沉积方法在LiB₃O₅基底上镀制了不加SiO₂内保护层和加SiO₂内保护层的倍频增透膜，测量了两类薄膜在波长1 064 nm多脉冲辐照下的激光损伤阈值，获得了两种不同的损伤形貌，并对损伤原因作了初步探讨。实验结果表明：保护层的加入把由基底膜层界面缺陷吸收所决定的阈值改变到由HfO₂膜层内缺陷吸收所决定的阈值，显著提高了倍频增透膜的抗激光损伤能力。     

波长1064nm脉冲激光高阈值反射膜的研制

 研究HfO₂/SiO₂高反射膜的制备工艺及其激光诱导损伤阈值的比较测试,分别采用了反应蒸镀HfO₂、反应离子辅助蒸镀HfO₂、反应离子辅助蒸镀金属Hf的源材料形成HfO₂薄膜。采用这三种工艺制备了HfO₂/SiO₂高反射膜,在中心波长1064nm处,反射率 R≥99.5%,其中反应蒸镀HfO₂/SiO₂高反射膜损伤阈值最高,可达60J/cm²(1064nm,5ns)。     

LBO晶体上1 064，532 nm倍频增透膜的镀制及性能分析

 用电子束蒸发沉积方法在X切LBO（X-LBO）晶体上镀制了两种不同膜系结构的1 064和532 nm倍频增透膜，其中一种膜系结构为基底/ZrO₂/Y₂O₃/Al₂O₃/SiO₂/空气，另一种为基底/0.5Al₂O₃/ZrO₂/Y₂O₃/Al₂O₃/SiO₂/空气，两种膜系结构的主要差别在于有无氧化铝过渡层。测量了薄膜的反射率光谱曲线，发现两种增透膜在1 064和532 nm处的反射率均小于0.5％，实际镀制结果与理论设计曲线的差异主要是由材料折射率的变化引起的。且对样品在空气环境中进行了温度为473 K的退火处理，结果发现两种膜系结构均表现了较优异的光学性能，氧化铝过渡层的加入使薄膜具有强的热应力性能。     

矿质氧化物表面过氧化氢的非均相过程研究

利用努森池反应器研究了过氧化氢与大气矿质氧化物的非均相过程,其初始摄取系数分别为(1.00±0.11)×10^-4 (σ-Al₂O₃)、(1.66±0.23)×10^-4 (MgO)、(5.22±0.9)×10^-5 (SiO₂)、(9.70±1.95)×1010^-5 (Fe₂O₃). 除SiO_{2相似文献}   

Picosecond laser ablation of SiO2 layers on silicon substrates

In this work, we report on laser ablation of thermally grown SiO₂ layers from silicon wafer substrates, employing an 8–9 ps laser, at 1064 (IR), 532 (VIS) and 355 nm (UV) wavelengths. High-intensity short-pulse laser radiation allows direct absorption in materials with bandgaps higher than the photon energy. However, our experiments show that in the intensity range of our laser pulses (peak intensities of <2×10¹² W/cm²) the removal of the SiO₂ layer from silicon wafers does not occur by direct absorption in the SiO₂ layer. Instead, we find that the layer is removed by a “lift off” mechanism, actuated by the melting and vaporisation of the absorbing silicon substrate. Furthermore, we find that exceeding the Si melting threshold is not sufficient to remove the SiO₂ layer. A second threshold exists for breaking of the layer caused by sufficient vapour pressure. For SiO₂ layer ablation, we determine layer thickness dependent minimum fluences of 0.7–1.2 J/cm² for IR, 0.1–0.35 J/cm² for VIS and 0.2–0.4 J/cm² for UV wavelength. After correcting the fluences by the reflected laser power, we show that, in contrast to the melting threshold, the threshold for breaking the layer depends on the SiO₂ thickness.     

Absorption of CO2 laser pulses at different wavelengths by ground-state and vibrationally heated SF6

The absorption of CO₂ laser pulses by low pressure SF₆ gas has been investigated over a wide range of energy fluxes. For laser energy fluxes of 0.01–1 J cm^-2 the effective absorption cross section varies between 0.2 and 2 × 10^-18 cm². For each laser line an individual dependence on the energy is found and in some cases minor changes in the absorption behaviour seem to occur around 0.1 J cm^-2. SF₆ excited with an average vibrational energy content of up to 20 photons/molecule does not absorb measurable amounts of 9.4 μm laser light. The influence of various SF₆ and Ar pressures on the temporal shape of the transmitted pulses has been investigated.     

Photo-acoustic and photo-refractive detection of small absorptions in liquids

The sensitivities of pulsed photo-acoustic and photo-refractive (e.g., thermal lensing) techniques for the measurement of small absorptions in liquids have been evaluated both theoretically and experimentally. Electrostriction limits the sensitivity of both techniques, this limitation is less severe for the photo-refractive technique. The minimum absorption constants observed experimentally, for a 200-μm laser spot size in liquid N₂, are 4 × 10^-5 cm^-1 for the photo-acoustic measurement and 6 × 10^-7 cm^-1 for the photo-refractive measurement. The calculated electrostrictive limits are 2 × 10^-5 cm^-1 and 7 × 10^-11 cm^-1, respectively.     

Optical properties of crystals doped with Sm3+ or Dy3+ relevant to potential InGaN/GaN laser diode-pumped visible laser operation: A comparative study

Results of detailed spectroscopic investigation of Sm³⁺ and Dy³⁺ ions incorporated in crystal structures of Yal YAl₃(BO₃)₄, LiNbO₃, Gd₃Ga₅O₁₂, Gd₂SiO₅, Lu₂SiO₅ and (Gd, Lu)₂SiO₅ are reported and discussed. The impact of the hosts on transition intensities and excited state relaxation dynamics of incorporated luminescent ions was examined. Distribution of luminescence intensity among spectral bands in terms of luminescence branching ratios was evaluated based on numerical integration of luminescence bands. Intensities of UV and blue absorption bands potentially useful for optical pumping were determined quantitatively in units of absorption cross section. The most intense luminescence bands related to potential laser transitions ⁴ G _5/2 → ⁶ H _7/2 of Sm³⁺ around 600 nm and ⁴ F _9/2 → ⁶ H _13/2 of Dy³⁺ around 580 nm were calibrated in units of emission cross section. Evaluated peak values of emission cross section range from 0.43 × 10^?20 cm² for Sm³⁺ in (Gd, Lu)₂SiO₅ to 1.17 × 10^?20 cm² for Sm³⁺ in LiNbO₃. Those for dysprosium-doped crystals range from 0.63 × 10^?20 cm² for LiNbO₃:Dy³⁺ to 2.0 × 10^?20 cm² for Yal YAl₃(BO₃)₄:Dy³⁺. It follows from these considerations that samarium-doped crystals show promise for laser application owing to the combination of a strong absorption that matches radiation of commercial laser diodes emitting near 405 nm and long luminescence lifetime. Major shortcoming of dysprosium-doped crystals results from a weak intensity of absorption bands available for optical pumping near 450 nm and 385 nm combined with relatively strong self-quenching of luminescence.     

Yb:Y2－2xLa2xO3激光透明陶瓷的光谱性能

对一种低温易烧结的Yb:Y_2-2xLa_2xO₃激光透明陶瓷的光谱性能进行了初步研究，Yb:Y_2-2xLa_2xO₃激光透明陶瓷具有宽的吸收带和大的吸收截面，在最强的吸收峰977nm处吸收截面达4.0×10^-20cm²；其荧光发射寿命为1.1ms，发射截面在1033nm处为1.0×10^-20cm²，在1077nm处为0.7×10^-20cm².Yb:Y_2-2xLa_2xO₃陶瓷的各项光学性能指标接近或达到单晶的指标. 关键词： 氧化镧钇 激光陶瓷 低温烧结 光谱性能     

Tm3+掺杂硅酸镓镧(La3Ga5SiO14)晶体的结构与光学性能研究

利用X射线粉末衍射确定了Tm³⁺掺杂硅酸镓镧(La₃Ga₅SiO₁₄,LGS)晶体的晶体结构;运用DICVOL91程序计算了该晶体不同部位的晶胞参数;测定了Tm：LGS晶体的室温吸收谱和470nm光激发下的发射光谱;根据Judd-Ofelt理论拟合了Tm³⁺的三个晶场调节参数Ω_t(t=2,4,6),分别为2.694×10^-20cm²,1.842×10^-20cm²,0.030×10^-20cm²;计算了各个能级跃迁的谱线强度、振子强度、吸收截面等,进而计算了³H₄和³F₄态的自发跃迁概率、辐射寿命、荧光分支比和积分发射截面,并对结果进行了分析. 关键词： Tm：LGS晶体 吸收谱 Judd-Ofelt理论 光谱参数     

Growth and laser properties of Nd<Superscript>3+</Superscript>:Sr<Subscript>6</Subscript>YSc(BO<Subscript>3</Subscript>)<Subscript>6</Subscript> crystal

The crystal of Nd³⁺:Sr₆YSc(BO₃)₆ with dimensions of O 19×42 mm³ was grown by the Czochralski method. It’s spectral and laser properties have been investigated. The absorption cross section is 1.47×10^-20 cm² with a FWHM 12.0 nm at 807 nm, the emission cross section is 1.57×10^-19 cm² at 1060 nm, and the fluorescence lifetime is 76 μs at room temperature. The maximum laser output is 25.7 mJ at 1.06 μm pumped by a single Xenon flash lamp and the overall and average slope efficiencies are 0.12% and 0.09%, respectively. The laser energy threshold value is 1.28 J. PACS 42.55.Rz; 42.70.Hj; 78.20.-e     

Rapid crystallization of silicon films using Joule heating of metal films

50-nm thick amorphous silicon films formed on glass substrates were crystallized by rapid Joule heating induced by an electrical current flowing in 100-nm-thick Cr strips formed adjacently to 200-nm-thick SiO₂ intermediate layers. 3-μs-pulsed voltages were applied to the Cr strips. Melting of the Cr strips caused a high Joule heating intensity of about 1×10⁶ W/cm². Raman scattering measurements revealed complete crystallization of the silicon films at a Joule heating energy of 1.9 J/cm² via the SiO₂ intermediate layer. Transmission electron microscopy measurements confirmed a crystalline grain size of 50–100 nm. 1-μm-long crystalline grain growth was also observed just beneath the edge of the Cr strips. The electrical conductivity increased from 10^-5 S/cm to 0.3 S/cm for 7×10¹⁷-cm^-3-phosphorus-doped silicon films because of activation of the phosphorus atoms because of crystallization. The numerical analysis showed a density of localized defect states at the mid gap of 8.0×10¹⁷ cm^-3. Oxygen plasma treatment at 250 °C and 100 W for 5 min reduced the density of the defect states to 2.7×10¹⁷ cm^-3. Received: 3 April 2001 / Accepted: 9 April 2001 / Published online: 25 July 2001     

Dipole formation and electrical properties of high-k/SiO2 interface according to the density of SiO2 interfacial layer

The effect of SiO₂ buffer layers with various atomic densities on the interface dipole of high-k/SiO₂ is confirmed. An ultrathin SiO₂ layer is formed on Si using the plasma-enhanced chemical vapor deposition (PECVD), H₂O₂ oxidation and nitric acid oxidation (NAOS). The atomic density ratio between the SiO₂ layer with various methods and the high-k is calculated respectively. As the oxygen density of the SiO₂ increased, the amount of the dipole and the flatband voltage (V_FB) shift decreased. Furthermore, leakage current density of the H₂O₂ (0.9 × 10⁻² A/cm²) due to the formation of low-density SiO₂, decreases by approximately six orders of magnitude when SiO₂ buffer layer is inserted using the NAOS (5.13 × 10^-8 A/cm²). Consequently, it is demonstrated that the dipoles that affects the V_FB shift is formed by the diffusion of oxygen ions between the high-k and SiO₂ interface, which has a significant effect of the MOS capacitor.     

Effect of higher order nonlinear optical processes on optical absorption in the photorefractive BSO and BGO crystals

The processes of nonlinear refraction and nonlinear absorption are studied in the photorefractive Bi₁₂SiO₂₀ (BSO) and Bi₁₂GeO₂₀ (BGO) crystals at a wavelength of a picosecond Nd:YAG laser of 1064 nm. The nonlinear refraction in the crystals is shown to be related to the Kerr effect, and the nonlinear absorption at this wavelength, to three-photon absorption. The three-photon absorption coefficients of the BSO and BGO crystals are equal, respectively, to (2.5±0.8) ×10^?20 and (4.4±1.3) ×10^?20 cm³W^?2.